Syria’s air force has repeatedly used cluster munitions to attack rebel-held areas, according to Human Rights Watch.
The weapons are controversial because, when released, they scatter dozens of smaller bomblets over a wide area.
Syrian activists have posted several videos showing bomb remnants which they claim have been dropped by regime helicopters.
Human Rights Watch has contacted residents in two towns to confirm the strikes.
Philippe Bolopion, the organisation’s United Nations Director, called on the Syrian government to immediately stop using the weapons.
“The cluster munitions that you can see in the videos are RBK-250, which is a Soviet made cluster munition. It’s obviously quite old. We are not sure how it ended up in Syria, but it is particularly dangerous because old munitions are less likely to detonate on impact and as a result, the duds that are left on the ground remain dangerous for civilians and kids, for weeks, months and sometimes years,” said Bolopion.
Activists say cluster bomb remnants were found in several towns in Idlib province and around Homs, Aleppo and the capital Damascus.
More than 110 countries – excluding the US – have signed a 2008 convention banning their production and use.